How can human hair be distinguished from animal hair? Human medullas have an index of < 1/3 while animal medullas have an index of > ½. Also, humans only have imbricate scales and can only have fragmented, continuous or absent medullas.
List and explain the three parts of the hair shaft. Cuticle—outside covering, made of overlapping scales. Cortex—inner layer made of keratin and embedded with pigment; also contains air sacs called cortical fusi. Medulla—inside layer running down the center of the cortex.
List the three growth phases of the hair and what each represents. Anagen—hair is actively growing; lasts up to 5 years; Catagen—hair is not growing; a resting phase; Telogen—follicle is getting ready to push the hair out; lasts two to six months